[kountzecobra]

George, I think I agree with a hp loss of 18 to 25%. Seems a of the late model Mustang crowd places the C4 trans at 18%, but the C6 internals weigh a LOT more so the numbers I have heard is 22-25%. Until I built this intaake manifold, I had never had any experience with two Holleys at one time. Luckily fuel distribution is quite even between cylinders according to sparkplug readings. I have done most all tuning up to this point by Seat-of-pants method. Drivability is nothing short of fantastic with only an occasional very small stumble, (Which I have lessened with accel. pump cams and different shooter sizes) when you go from a slow cruise to WOT without downshifting. I don't consider this a problem as with this car I don't often need that rate of acceleration. I have tried many different setups on the carb linkage and the best drivability is with both carbs opening together. Did I mention these are 390 cfm Holleys. Also I now have the "plain" secondary springs (very stiff) in both carbs. I do enjoy a discussion like this. Anyone with some suggestions to try?